It is known from the prior art how to use electric heating units or heating units having electric heating elements arranged in a washing machine barrel of a washing machine underneath a drum. They can be used to heat up water to a required temperature, for example, needed for washing. Usually so-called tubular heaters are used for this purpose, however planar heating elements can also be used.
A problem underlying the invention is to provide a method as mentioned at the outset in which drawbacks in the prior art can be overcome. In particular, the scope of functioning of a washing machine can be expanded without major effort and preferably the heating unit can be used for other purposes.
This problem is solved by a method having the features as claimed herein. Advantageous and preferred embodiments of the invention form the subject matter of the further claims and are explained in greater detail in the following. Some of the features are explained only for the method, the heating unit, or the washing machine. They should however, regardless of this, be applicable for the method. The wording of the claims is made into part of the substance of the description by express reference.
It is provided that the heating unit has a carrier, and at least one planar heating element arranged thereon. The heating element is attached in planar manner to the carrier, where above all the planar or planar-running character of the heating element is important. The carrier has in one region, advantageously in a central region, a recess running over a considerable length or along the carrier. As a result, it is possible, as explained in further detail in the following, to achieve a defined flow of the water off the carrier. Furthermore, a certain concentration of water can be achieved in a certain region in order to permit here, for example, particularly selective and efficient evaporation or heating. The previously described heating unit is arranged at the barrel bottom inside a washing machine barrel between its lower region and the drum. A possible curved form of the heating unit can advantageously be used so that the distance between the drum and the washing machine barrel does not have to be too large. The curvature or radius of the heating unit can match that of the washing machine barrel.
In accordance with one embodiment of the invention, steam is generated in the washing machine or with the heating unit. To do so, only one heating element that is in the region of the recess is operated, as has already been described. This has the effect on the one hand of saving energy, since other heating elements adjacently arranged which normally have less water in their vicinity are not operated as they would be less efficient, contributing considerably less to steam generation. Furthermore, it is in the recess in particular that water can be supplied in, so it can be heated particularly well until evaporation. Here too, a temperature and hence the evaporation can be regulated as well as possible using a temperature sensor. Furthermore, the water intended for evaporation can be supplied to, or sprayed into, the heating unit by an appropriate pump or another similar device in such a way that it collects inside the recess and is completed evaporated before it flows off.
In another embodiment of the invention, the carrier can have in its longitudinal course a longitudinal channel as the stated recess. The longitudinal channel can, as a general principle, have any required design, but is advantageously rounded. It is particularly advantageous when the entire carrier is substantially curved or rounded with a channel form or in the shape of a spade or semi-circular form, and forms the recess itself by its shape. A curvature can be designed substantially uniformly, in particular even over the entire length of the carrier. This means therefore that the water can run off the carrier in the form of a channel particularly well or can previously collect inside it as well as possible. Although it is possible in principle to provide several recesses on the carrier, a single recess is preferred.
The heating unit after installation inside the washing machine can slope in its longitudinal course, preferably slightly obliquely, so that water on it can run off. For this purpose, the channel formed is advantageous here too, since it both effects a certain quantitative concentration of the water on it, or flowing onto it, and also permits a good flow-off. It is particularly advantageous when the heating unit slopes towards its free end. The heating unit can here be advantageously installed such that it runs in its longitudinal direction or in the direction of the recess approximately parallel to a rotation axis of the drum.
Like the recess, at least one heating element of the carrier extends advantageously over its main length. A heating element of this type can be provided either as a full surface, or cover a surface and be designed for example in a meandering shape.
Although it is possible, as a general principle, to provide heating elements on both sides of the carrier, advantageously one heating element is provided on the outside, i.e., topside of the carrier, i.e., in the region where the recess projects beyond the course of the carrier, or along an apex, or along an apex line of the recess. In this way it can be achieved that when the heating unit is installed in the washing machine, the recess or its said apex line forms the lowest point of the heating unit. This is where the water collects. The water can run off on one side; however in any event it is in this region in which the water remains longest that the heating element is arranged for optimum heating up or evaporation of this water. The arrangement of the heating element on the outside of the carrier or in the installed state on the underside also has the advantage that lime deposits or the like are not directly present on the heating element, but only on the carrier surface. It is particularly advantageous when all heating elements are provided on the same side, i.e., on the outside or underside.
In another embodiment of the invention, at least one first heating element is provided as stated above inside the region of the recess, and at least one second heating element is located adjacently towards the lateral edge or longitudinal side of the carrier. It is particularly advantageous when second heating elements are provided on both sides of the first heating element and in particular are designed identically and of identical size. It is advantageous here when the first heating element and the second heating elements can each be operated separately from one another depending on the required operating mode. This is described in more detail in the following section.
In another embodiment of the invention, a temperature sensor can be provided on the carrier. This too can be designed using thick-film technology. The temperature sensor is, like the heating elements, advantageously provided on the carrier on the outside or underside of the recess, in particular precisely at the recess. In this way, the temperature sensor can measure the temperature of the heating unit and above all of the heating element at the recess, and a water temperature can be deduced from this when the heating element is completely immersed in water for heating mode or for determining a temperature for evaporation mode. In another embodiment of the invention, two such temperature sensors are provided, both on the same side. It can here be advantageous to provide the temperature sensors in each case close to one end of the carrier, in particular in each case at the recess. This enables the temperature of the heating unit to be well regulated particularly during the evaporation mode in accordance with the invention. An alternative possibility for temperature measurement or as a substitute for the temperature sensors is to measure the electric resistance of the heating unit, as is generally known to a person skilled in the art. This electric resistance can be an NTC (negative temperature coefficient) or a PTC (positive temperature coefficient) resistor in particular for better measurement.
In a further embodiment of the invention, a conductivity measuring device can be provided on the carrier. It can for example be designed using thick-film technology and have two electrodes covered by a top layer and protected against the washing liquid or washing suds. Such conductivity measuring devices are generally known from the prior art, see for example U.S. Pat. No. 7,613,385 or U.S. Pat. No. 7,705,603. This conductivity measuring device can be used to ascertain properties of the washing liquid in particular the degree of soiling or the like.
In a further embodiment of the invention, the carrier can have a function layer. This can for example have an anti-stick effect, in particular in the manner of a PTFE (polytetrafluoroethylene) layer. Further functions can be insulating properties for electrical insulation or resistance to aggressive media such as water, steam or lime, in particular in the washing liquid. An above function layer with anti-stick effect is advantageous particularly on the upper side of the heating unit, so that no deposits can form from the water on it.
A heating capacity of slightly less than 1000 W can be achieved by the heating unit at the heating element along the recess. The heating capacity is advantageously less than 800 W, since the switching or cycling of the individual heating elements is possible as often as required in accordance with the regulations of the energy suppliers. A total capacity of up to more than 2000 W can be achieved by heating elements arranged adjacently.
In a further operating mode of the heating unit or washing machine, it can be operated such that the water in the washing machine or in the washing machine barrel is to be heated for a washing operation. All heating elements of the heating unit are then advantageously operated/controlled, their precise operation being handled by the above temperature sensors.
These and further features can be gathered from the claims, description and drawings, where the individual features, both singly or severally in the form of subcombinations, can be implemented in an embodiment of the invention and in other fields and can represent advantageous and independently protectable designs for which protection is claimed here. The subdivision of the application into individual sections and the subheadings in no way restrict the general validity of the statements made thereunder.